Electrical pulse transmitting apparatus



April 7, 9 r s. A. ANDREWS ET AL 3,504,538

ELECTRICAL PULSE TRANSMITTING APPARATUS Filed Sept. 27, 1967 l 3Sheets-Sheet 1 INVENTORS Mote: w. Ltwus.

April 7, 1970 s. A. ANDREWS ET M- 5 5 ELECTRICAL PULSE TRANSMI'II.".IINGAPPARATUS Filed Sept. 27, 19s! I s Sheets-Sheet INVENTORS STUART Moan:w. Lew

April 7, 1970 s. A. ANDREWS ET AL 5 53 ELECTRICAL PULSE TRANSMITTINGAPPARATUS Filed Sept. 27, 1967 'SSheetS-Sheet 3 INVENTORS swam- A.Auuuwa Mona: w. Liwls.

United States Patent US. Cl. 73136 8 Claims ABSTRACT OF THE DISCLOSUREElectrical pulse-transmitting apparatus. for determining changes inrelative rotational positions of two continuously rotatable coaxialmember's, connected to axially spaced points in a torque shaft whereinthe two rotatable members have equal numbers of circumferential teethand are surrounded by annular stators which have equal numbers ofcircumferential teeth and are associated with pick-up coils by whichelectrical pulses produced by changes in magnetic flux in therstatorsare transmitted to apparatus analysing the phase relationship betweenthe pulses from the two coils.

This invention relates to electrical pulse transmitting apparatus foruse in determining changes in the relative rotational positions of twocontinuously rotatable coaxial members by measuring changes in phasebetween the pulses transmitted by elect romagnetic pick: up devicesassociated respectively with the two rotatable coaxial members, and isparticularly but not exclusively applicable to electrical pulsetransmitting apparatus for 3,504,538 Patented Apr. 7, 1970 "ice -Moreover the two stators, their associated magnets and pick-up coilsare'conveniently rigidly connected to one another in coaxialrelationship so as to avoid as far as possible any risk of the twostators and pick-ups moving relatively to one another about the commonaxis of rotation of the two rotary members due, for example, tomechanical and/ or thermal distortion.

The number of teeth on each rotary member may in some cases be the sameas, or a multiple of or exactly divisible by, the number of teeth oneach stator so that the number of pulses transmitted by each pick-upduring each revolution of the associated rotary member is equal to thenumber of teeth in that one of the two circumferential rows having thegreater number of teeth. Alternatively the number of teeth on eachrotary member may be different from, and not a multiple of or exactlydivisible by, the number of teeth on each stator so that the number ofpulses transmitted by each pick-up during each revolution of theassociated rotary member is a multiple of the number of teeth on therotary member orits associated stator. Moreover in the latter case in apreferred example each rotary member has one more or one less tooth thaneach stator, so that the number of pulses transmitted by each pick-upduring each revolution of each rotary member is the product of thenumber of teeth on the rotary member multiplied by the number of teethon the stator.

It will be apparent that for given over all dimensions includingapproximate tooth dimensions the former arrangement will provide pulsesof relatively large amplitude but few in number per revolution, comparedwith the latter arrangement which will provide pulses of reuse in torquemeters of the-kinda in which thetwo continuously rotatable coaxialmembers are'connected at axially spaced points to a torque shaft subjecttothe torque tobe measured so that the degreepf relative rotationalmovement between the two continuously rotatable co.- axial memberscorresponds to changes in the torque transmitted.

U Pulse transmitting apparatus of various kinds-has been proposed forthe above purpose, and it is an object of the present invention toprovide an improved form of such pulse transmitting apparatus which willlend itself toac curate measurement of the degree'of relativerotationalmovement which occurs between the continuously rotatable coaxialmembers. V

To this end electrical pulse transmitting apparatus, ac-

cording to the present invention for determiningchanges in the relativerotational positions of two continuously rotatable coaxial memberscomprises rotary members connected respectively'to the two rotatablemembers and each in the form of a ring of magnetic material having acircumferentially extending row of equally spaced teeth,

an annular stator of magnetic material coaxial with each rotary memberand also provided with a circumferentially extending row of equallyspaced teeth lying adjacent to the teeth on the associated rotarymember, and electromagnetic pick-up means (hereinafter referred to forconvenience as a pick-up) associated with each stator and arranged totransmit through associated electrical conductors a series of electricalpulses resulting from changes in magnetic flux in its. associated statoras its associated rotary member rotates. I

Preferably each pick-up comprises an annular axially polarized magnet,formed as a continuous ring or in two or more segments, disposedcoaxially with its associated stator, and at least one annular pick-upcoil arranged coaxially with the stator and magnet.

latively small amplitude but considerably greater in number pe'rrevolution. It is thus possible to employ one arrangement or the otheraccording to whether it is desired to have comparatively high amplitudepulses for feeding to "the electrical analysing apparatus whichdetermines and'i'ndicates the phase relationship between'the pulses fromthe two pick-up devices and tolerate the fact that small degrees ofrelative rotation between the two rotary members will only result inrelatively small phase changes between the pulses, or to have a largenumber of pulses of small amplitude per revolution for feeding to theanalysing apparatus and tolerate the fact that analysing apparatussensitive to such small amplitude pulses will tend to be more sensitivethan that designed to analyse pulses of large amplitude, while it willtend also to be more influenced by any affects on the pulse transmissionwhich may occur due to vibration or other causes..-

When the invention is applied to a torque meter. the two rotary membersconveniently lie adjacent to one another and adjacent to the same end ofa torque shaft, to-which end one of the rotary members is directlyattached, while the other rotary member. is connected to the other endof the torque shaft by means of a tubular memher which surrounds and iscoaxial with the torque shaft. In this case the tubular member may beconnected to the torque shaft by coupling means comprising externalsplines on the torque shaft engaging internal splines on the appropriateend portion of the tubular member, which end portion is splitlongitudinally, and a clamping ring surrounding the split internallysplined portion of the tubular number and maintaining the splines withinthe tubular member in close engagement with the splines on the adjacentend of the torque shaft. In such a construction, in which the clampingring may be an unsplit ring closely surrounding and gripping the splitpart of the tubular member as by being shrunk on to it, not only isbacklash between the internally splined end of the tubular member andthe plines on the torque shaft prevented but the axial length of theinternal splines on the tubular member and/or the external splines onthe torque shaft can be short so that the length of the part of thetorque shaft extending between its effective points of connectionrespectively to the two rotary members can be exactly determined. 7

The two rotary members will in any case conveniently be provided withparts having coaxial interengaging surfaces serving to support the tworotary members in coaxial relationship with one another while permittingthe required degree of relative rotational movement.

One construction according to the invention as applied to a torque meteris shown by way of example in the accompanying drawings, in which: I

FIGURE 1 is a sectional side elevation of one form of pulse-transmittingapparatus according to the invention as applied to a torque meter,

FIGURE 2 is a cross-section on the line 22 of FIG- URE 1,

FIGURE 3 is a cross-section on the line 33 of FIGURE 1,

FIGURE 4 is a cross-section on the line 5-5 of FIG- UR'E 1,

FIGURE 5 is a side elevation showing a detail of the arrangement shownin FIGURE 4, and

FIGURE 6 is a cross-section similar to FIGURE 2 showing a modified formof the invention.

In the construction shown in FIGURES 1, 2, 3, 4 and 5 the pulsetransmitting apparatus is applied to a torque shaft assembly comprisinga hollow driving shaft 1 connected by internal splines to splines 2 onone end of a hollow torque shaft 3 the other end of which is integralwith a driven shaft 4. The driving shaft 1 has a tubular extension 6into which extends freely one end of a tubular member 7. Rigid with, andforming ineffect part of the tubular member 7 within the extension 6 isa tubular coupling element 8 which is split longitudinally at 9 as shownin FIGURES 4 and 5 and provided with a short ring of internal splines 10engaging the adjacent ends of the splines 2. Shrunk onto the end of thecoupling element 8 is a ring 11 which serves to maintain the splined endof the part 8 in close engagement, without backlash, with the splines 2.

Formed at the left hand end of the torque shaft 3 where it joins thedriven shaft 4 is a rotary member in the form of a shallow flange 12having formed thereon a circumferential row of equally spaced teeth 13,While there is attached to the end of the tubular member 7 adjacent tothe flange 12 a rotary member 14 provided with a circumferential row ofequally spaced teeth equal in number to the teeth 13.

It will thus be seen that the torque shaft 3 transmits torque from thedriving shaft 1 to the driven shaft 4 and that changes in the torquetransmitted will cause corresponding changes in the relative rotationalpositions of the flange 12 and the part 14 and hence of the teeth 13 and15. Moreover, the short axial length of the internal splines 10 enablesthe effective axial length of the torque shaft 3 to be determined withaccuracy while, backlash between the engaging splines 10 and 2 beingprevented, the rotational position of the flange 12 relatively to thepart 14 at any moment during transmission of torque as compared with therelative rotational position of these parts under zero torque conditionstends to be an accurate measure of the torque being transmitted.

The shaft 4 and hence the flange 12 and teeth 13 are of steel, as alsoare the member 14 and its teeth 15, and the two circumferential rows ofteeth 13 and 15 are surrounded by a station [assembly comprising twopick-up units rigidly secured to opposite sides of a spacer ring 16 ofnon-magnetic material, each unit surrounding one of the rows of teeth 13and 15. Each of the pick-up units comprisesa plate 18 of magneticmaterial having a circumferentially extending row of equally spacedteeth 18A formed on its inner periphery, and a similar plate 19 ofmagnetic material without teeth, the number of teeth in each row 18Abeing one more or one less than the number of teeth in each of the rows13 and 15. Interposed between each of the pairs of plates 18, 19 is anannular pick-up coil 20 surrounded by an annular axially polarizedpermanent magnet 21 which may be formed as a unit or in segments.

Conductors, indicated at 22, 23, from the pick-up coils 20 are providedfor connection to electronic apparatus 23A which may be of known type,and by which the phase relationship between electrical pulses receivedrespectively from the two pick-up coils 20 can be analysed and indicatedso as to determine the degree, if any, to which at any moment the rowsof teeth 13 and 15 have been displaced rotationally relatively to oneanother from their zero torque position, hence the torque beingtransmitted.

In the example shown, as indicated in FIGURES 2 and 3 each of the ringsof teeth 13 and 15 might comprise say 30 teeth while each of the plates18 is provided with 31 internal teeth. It will thus be seen that foreach revolution of each of the. rotary members 12 and 14 with their rowsof teeth 13 and 15, there will be transmitted from each of the pick-upcoils 20, 930 pulses (i.e. 30 multiplied by 31). Assuming, therefore,that each pulse cycle from either pick-up coil is regarded asrepresented by an angle of 360 a phase change of 360 between the pulsesfrom one pick-up coil and those from the other will be produced by atwist in the torque shaft of only 0.387 degree.

In the modification shown in FIGURE 6, each of the rings of teeth 13A,15A comprises 30 teeth while each of the plates 18 is also provided with30 internal teeth 183. For each revolution of each of the rotary members12 and 14 in this construction therefore, there will be transmitted fromeach of the pick-up coils, 20, only 30 pulses, but for given dimensions,the pulses will be of high amplitude, compared with those provided bythe construction shown in FIGURE 3. Moreover in either construction,without altering the over-all dimensions of the pulsetransmittingdevices, the number of teeth on the rotary members 12 and 14, can bereduced or increased and the dimensions of each tooth thus respectivelyincreased or reduced to provide respectively greater amplitude but lesssensitivity to small changes in torque or greater sensitivity to suchsmall changes but less amplitude, according to the requirements of anyparticular application. Thus, if a large number of pulses for eachrevolution is desired to provide large changes in phase relationshipwith small degrees of relative rotation between the rotary memberssensitivity can be obtained in this way by employing one more tooth oneach of the members 13 and 15 than on the plates 18, and/or by providinga large number of comparatively small teeth on the members 13 and 15 andthe plates 18. Whereas if it is desired to provide a relatively smallnumber of pulses of higher amplitude but at some sacrifice ofsensitivity this can be achieved by employing the same number of teethon the members 13 and 15 and the plates 18 and/or a comparatively smallnumber of large teeth on all these members.

It will be seen that in any case the general arrangement provides forrigid connection into a single assembly of the two pick-up units inco-axial relationship with each other while moreover the rotary member14 can be firmly held substantially concentric with the flange 12 bymeans of a sleeve 24 relative to which it can rotate. The risk ofchanges in phase relationship between the pulses from other rotarymember is connected to the other end of the troque shaft by means of acoupling member which is held in a bearing which supports it from, andcoaxially with, the said one end of the torque shaft, each rotary memberbeing in the form of a ring of magnetic material having acircumferentially extending row of equally spaced teeth, the apparatusalso including an annular stator coaxial with each rotary, member, andhaving electro-magnetic pickup means arranged to transmit throughassociated electrical conductors a series of electrical pulses resultingfrom changes in magnetic flux as the rotaryme-mbers rotate, andelectrical analyzing and indicating apparatus connected to the saidelectrical conductors to analyze and indicate the phase relationshipbetween the two series of pulses. Y

2. Electrical pulse-transmitting apparatus as claimed in claim 1, in:which each pick-up means. comprises an annular magnet, formed as acontinuous ring or in two or more segments, disposed coaxially with itsassociated stator, and iat least one annular picil l-up coil arrangedcoaxially with the stator and magnet'and connectedto saidassociatedfilectrical conductors.

3. Electrical pulse-transmitting apparatus as claimed in claim 2 inwhichthe magnet is axially polarized.

4. Electrical pulse-transmitting apparatus as claimed in claim 1, 'inwhich the stator has teeth and the number of teeth on each rotary memberis the same as or a mnltiple of or exactly divisible by the number ofteeth on the stator whereby the number of .pulses transmitted by thepick-up means during each revolution of the associated rotary member isequal to the number of teeth in the circumferential row having thegreater number of teeth.

5. Electrical pulse-transmitting apparatus as claimed in claim 1, inwhich the stator has teeth and the number of teeth on each rotary memberis different from and not a multiple of or exactly divisible by thenumber of teeth on the stator, so that the number of pulses transmittedby the pick-up device during each revolution of the associated rotarymember is a multiple of the number of teeth on the rotary member or thestator.

6. Electrical pulse-transmitting apparatus as claimed in claim 5, inwhich each rotary member has one more or one less tooth than the statorso that the number of pulses transmitted by each pick-up device duringeach revolution of each rotary member is the product of the number ofteeth on the rotary member multiplied by the number of teeth on thestator.

7. Electrical pulse-transmitting apparatus as claimed in claim 1, inwhich the end of the coupling member remote from the rotary member towhich it is attached is connected to the torque shaft by coupling meanscomprising external splines on the torque shaft engaging internalsplines 0n the appropriate end portion of the coupling member, which endportion is split longitudinally, and a clamping ring surrounding thesplit internally splined portion of the coupling member and maintainingthe splines within the coupling member in close engagement with thesplines on the adjacent end of the torque shaft.

8. The electrical pulse-transmitting apparatus as claimed in claim 1 inwhich the end of the coupling member remote from the rotary members isconnected to the other end of the torque shaft by coupling meanscomprising external splines.

References Cited UNITED STATES PATENTS 2,349,663 5/1944 Langer 73-1362,824,245 2/1958 Trevitt 310-168 3,295,367 1/1967 'Rundell 73-136FOREIGN PATENTS 605,716 7/ 1948 Great Britain. 627,565 8/ 1949 GreatBritain.

CHARLES A. RUEHL, Primary Examiner US. Cl. X.R.

